Dead tank circuit breakers are commonly found in substations and are operable to selectively open and close electrical connections contained within a sealed tank filled with dielectric material for reducing arcing.
Despite careful manufacturing practices, an assembled circuit breaker can contain undesirable foreign particles such as metal shavings from machined parts, dirt, etc. It is undesirable for these particles, especially metallic, electrically conductive particles to reside in the tank since, if such particles are permitted to remain free in the tank, they could cause undue arcing, flashing, or can be electrically charged and radially reciprocate within the tank, reducing the breakdown voltage of the circuit breaker.
Particle traps have been developed for trapping these foreign particles. Conventional particle traps are configured in two ways: external and integrated. External particle traps are components that are fixed to the tank in some manner to shield particles in the bottom of the tank from the electric field. Integrated particle traps are a cast feature and typically includes a single trough (running radially), a single cup, or single trough (running lengthwise of the tank) used to catch particles.
Cups and troughs are susceptible to the electrical field reaching into the protected area and generating activity. A trough running with the tank length can always permit the electric field to enter. There are ways to avoid the field from entering the cup and the radial trough, such as making the depth significantly deeper than the width. This is not possible on some dead tank circuit breakers due to height restrictions. Therefore, another method is to minimize the width of the trap such that the depth to width ratio is optimized. However, this method leads to a greater probability of particles not entering the integrated trap.
Thus, there is a need to provide particle trap structure in a tank of a dead tank circuit breaker that allows for a large catch width while reduces the need for depth, which reduces the cost of the particle trap and increases performance by catching more particles without increasing tank diameter.